AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Size and Volatility of Vehicle Emitted Primary Particles Measured in a Traffic Tunnel
XIANG LI, Timothy Dallmann, Andrew May, Albert A. Presto, Carnegie Mellon University
Abstract Number: 576 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract On-road gasoline and diesel vehicles are a major source of several gaseous and particulate pollutants to the atmosphere, including CO, NOx, volatile organic compounds (VOCs), and particulate matter (PM). This poster presents multi-seasonal measurements of gas- and particle-phase pollutants from a traffic tunnel in Pittsburgh, PA. Using data from this field campaign, 1) we update the vehicle emissions factors of CO, NOx, particle phase Organic Carbon(OC) and Elemental Carbon(EC); 2) we provide size-distributions of vehicle emitted particles and their non-volatile components using a nano-SMPS and a long-SMPS together with a Thermodenuder(TD); and 3) we quantify the volatility of vehicle-emitted primary organic aerosol (POA) with a thermodenuder (TD) and an Aerodyne Aerosol Chemical Speciation Monitor (ACSM), as well as quartz filter samples analyzed by a thermal-desorption gas-chromatography mass-spectrometry (TD-GC-MS).
The measured emission factors are compared with emission factors measured in another tunnel study conducted in Pittsburgh 10 years ago, and the NOx, OC and EC emission factors of heavy duty diesel vehicles (HDDV) are ~30–50% lower. After evaporating under 250 °C inside TD, the nonvolatile PM appeared at two modes downstream of the TD – one consisting of EC with a peak at 80-100 nm, and another consisting of particles smaller than 10 nm. The chemical composition of the ~10 nm mode is uncertain. Our size-distribution measurements also suggest that smaller particles (less than 30 nm) emitted by vehicles are dominantly (over 90%) composed of volatile compounds.